A parent has taken a teacher hostage and is barricaded inside Castle View Elementary School in Riverside, school district officials said Tuesday.

The district was notified about the situation just after 11:20 a.m., Riverside Unified spokesman Justin Grayson said.

The door to a room is blocked with the male parent and a female teacher inside, said Riverside Police Officer Ryan Railsback. It was not immediately clear which room the man and hostage were in.

The incident began when the parent arrived before 11:15 a.m. and got into a confrontation with a teacher, Railsback said. The parent did not appear to follow the school district’s safety procedures and check in with the front desk, he added.

On campus, the parent was confronted by a male teacher and the parent struck that teacher in the face, Railsback said. A witness told KABC that the teacher’s face was bloodied and his nose was broken. The teacher was treated at a nearby hospital, police said.

The parent then went into a classroom and took a female teacher hostage, police said. The two have been in there ever since.

“He’s not responding to our commands to come out so far,” Railsback said. Witnesses did not report seeing any weapons on the man, police said.

Smoke was briefly seen coming out of the room, but Railsback said he didn’t have any information about it. It did not appear to be toxic, he said.

Police evacuated all students from the campus and began releasing them to their parents after 1 p.m. All students were accounted for, Grayson said. It was not immediately clear whether the man had a firearm.

Officials said students would be released to parents or guardians with proper photo identification.